At 19, Davis was so inspired by a trip to an orphanage in Uganda that she dropped a bombshell on her Brentwood, Tennessee, family: She was moving there.

What she's done since is breathtaking. Davis' nonprofit, Amazima Ministries International, connects 600 vulnerable children with sponsor families worldwide and feeds 1,500 kids a week. Davis herself is adopting 13(!) daughters, ages 4 to 16—a feat she chronicles in her memoir, Kisses From Katie. "I never intend anyone to think, Wow, I want to do what she does," says Davis. "Service is just about saying yes to the people around you who need your help."